Bone treatment systems and methods

ABSTRACT

The present invention relates in certain embodiments to medical devices for treating osteoplasty procedures such as vertebral compression fractures. More particularly, embodiments of the invention relate to instruments and methods for controllably restoring vertebral body height by controlling the geometry of fill material introduced into cancellous bone. A method of treating bone includes injecting a volume of fill material into a bone and selectively modifying a viscosity of the bone filler to control the direction of flow of the fill material within the bone. A system for treating bone using this method includes an introducer for delivering fill material into the bone and an energy source selectively coupleable to the fill material to alter the viscosity of the fill material via an energy emitter in the introducer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/165,652,filed on Jun. 24, 2005 which claims the benefit of priority under 35U.S.C. §119(e) of U.S. Provisional Application Ser. No. 60/633,509 filedDec. 6, 2004, entitled “BONE FILL MATERIALS AND METHODS OF USE FORTREATING VERTEBRAL FRACTURES.” This application is also related to U.S.patent application Ser. No. 11/165,651, filed Jun. 24, 2005, entitled“BONE TREATMENT SYSTEMS AND METHODS.” The entire contents of the aboveapplications are hereby incorporated by reference and should beconsidered a part of this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in certain embodiments to medical devicesfor treating osteoplasty procedures such as vertebral compressionfractures. More particularly, embodiments of the invention relate toinstruments and methods for controllably restoring vertebral body heightby controlling the geometry of fill material introduced into cancellousbone. An exemplary system utilizes Rf energy in combination a conductivebone fill material for polymerizing the surface of the inflow plume tocontrol the geometry of the fill material and the application of forcecaused by inflows of fill material.

2. Description of the Related Art

Osteoporotic fractures are prevalent in the elderly, with an annualestimate of 1.5 million fractures in the United States alone. Theseinclude 750,000 vertebral compression fractures (VCFs) and 250,000 hipfractures. The annual cost of osteoporotic fractures in the UnitedStates has been estimated at $13.8 billion. The prevalence of VCFs inwomen age 50 and older has been estimated at 26%. The prevalenceincreases with age, reaching 40% among 80-year-old women. Medicaladvances aimed at slowing or arresting bone loss from aging have notprovided solutions to this problem. Further, the population affectedwill grow steadily as life expectancy increases. Osteoporosis affectsthe entire skeleton but most commonly causes fractures in the spine andhip. Spinal or vertebral fractures also cause other serious sideeffects, with patients suffering from loss of height, deformity andpersistent pain which can significantly impair mobility and quality oflife. Fracture pain usually lasts 4 to 6 weeks, with intense pain at thefracture site. Chronic pain often occurs when one vertebral level isgreatly collapsed or multiple levels are collapsed.

Postmenopausal women are predisposed to fractures, such as in thevertebrae, due to a decrease in bone mineral density that accompaniespostmenopausal osteoporosis. Osteoporosis is a pathologic state thatliterally means “porous bones”. Skeletal bones are made up of a thickcortical shell and a strong inner meshwork, or cancellous bone, ofcollagen, calcium salts and other minerals. Cancellous bone is similarto a honeycomb, with blood vessels and bone marrow in the spaces.Osteoporosis describes a condition of decreased bone mass that leads tofragile bones which are at an increased risk for fractures. In anosteoporosis bone, the sponge-like cancellous bone has pores or voidsthat increase in dimension making the bone very fragile. In young,healthy bone tissue, bone breakdown occurs continually as the result ofosteoclast activity, but the breakdown is balanced by new bone formationby osteoblasts. In an elderly patient, bone resorption can surpass boneformation thus resulting in deterioration of bone density. Osteoporosisoccurs largely without symptoms until a fracture occurs.

Vertebroplasty and kyphoplasty are recently developed techniques fortreating vertebral compression fractures. Percutaneous vertebroplastywas first reported by a French group in 1987 for the treatment ofpainful hemangiomas. In the 1990's, percutaneous vertebroplasty wasextended to indications including osteoporotic vertebral compressionfractures, traumatic compression fractures, and painful vertebralmetastasis. Vertebroplasty is the percutaneous injection of PMMA(polymethylmethacrylate) into a fractured vertebral body via a trocarand cannula. The targeted vertebra is identified under fluoroscopy. Aneedle is introduced into the vertebral body under fluoroscopic control,to allow direct visualization. A bilateral transpedicular (through thepedicle of the vertebra) approach is typical but the procedure can bedone unilaterally. The bilateral transpedicular approach allows for moreuniform PMMA infill of the vertebra.

In a bilateral approach, approximately 1 to 4 ml of PMMA is used on eachside of the vertebra. Since the PMMA needs to be forced into thecancellous bone, the techniques require high pressures and fairly lowviscosity cement. Since the cortical bone of the targeted vertebra mayhave a recent fracture, there is the potential of PMMA leakage. The PMMAcement contains radiopaque materials so that when injected under livefluoroscopy, cement localization and leakage can be observed. Thevisualization of PMMA injection and extravasation are critical to thetechnique—and the physician terminates PMMA injection when leakage isevident. The cement is injected using syringes to allow the physicianmanual control of injection pressure.

Kyphoplasty is a modification of percutaneous vertebroplasty.Kyphoplasty involves a preliminary step consisting of the percutaneousplacement of an inflatable balloon tamp in the vertebral body. Inflationof the balloon creates a cavity in the bone prior to cement injection.The proponents of percutaneous kyphoplasty have suggested that highpressure balloon-tamp inflation can at least partially restore vertebralbody height. In kyphoplasty, some physicians state that PMMA can beinjected at a lower pressure into the collapsed vertebra since a cavityexists, when compared to conventional vertebroplasty.

The principal indications for any form of vertebroplasty areosteoporotic vertebral collapse with debilitating pain. Radiography andcomputed tomography must be performed in the days preceding treatment todetermine the extent of vertebral collapse, the presence of epidural orforaminal stenosis caused by bone fragment retropulsion, the presence ofcortical destruction or fracture and the visibility and degree ofinvolvement of the pedicles.

Leakage of PMMA during vertebroplasty can result in very seriouscomplications including compression of adjacent structures thatnecessitate emergency decompressive surgery. See “Anatomical andPathological Considerations in Percutaneous Vertebroplasty andKyphoplasty: A Reappraisal of the Vertebral Venous System”, Groen, R. etal, Spine Vol. 29, No. 13, pp 1465-1471 2004. Leakage or extravasationof PMMA is a critical issue and can be divided into paravertebralleakage, venous infiltration, epidural leakage and intradiscal leakage.The exothermic reaction of PMMA carries potential catastrophicconsequences if thermal damage were to extend to the dural sac, cord,and nerve roots. Surgical evacuation of leaked cement in the spinalcanal has been reported. It has been found that leakage of PMMA isrelated to various clinical factors such as the vertebral compressionpattern, and the extent of the cortical fracture, bone mineral density,the interval from injury to operation, the amount of PMMA injected andthe location of the injector tip. In one recent study, close to 50% ofvertebroplasty cases resulted in leakage of PMMA from the vertebralbodies. See Hyun-Woo Do et al, “The Analysis of PolymethylmethacrylateLeakage after Vertebroplasty for Vertebral Body Compression Fractures”,Jour. of Korean Neurosurg. Soc. Vol. 35, No. 5 (May 2004) pp. 478-82,(http://www.jkns.or.kr/htm/abstract.asp?no=0042004086).

Another recent study was directed to the incidence of new VCFs adjacentto the vertebral bodies that were initially treated. Vertebroplastypatients often return with new pain caused by a new vertebral bodyfracture. Leakage of cement into an adjacent disc space duringvertebroplasty increases the risk of a new fracture of adjacentvertebral bodies. See Am. J. Neuroradiol. 2004 February; 25(2):175-80.The study found that 58% of vertebral bodies adjacent to a disc withcement leakage fractured during the follow-up period compared with 12%of vertebral bodies adjacent to a disc without cement leakage.

Another life-threatening complication of vertebroplasty is pulmonaryembolism. See Bernhard, J. et al, “Asymptomatic diffuse pulmonaryembolism caused by acrylic cement: an unusual complication ofpercutaneous vertebroplasty”, Ann. Rheum. Dis. 2003; 62:85-86. Thevapors from PMMA preparation and injection also are cause for concern.See Kirby, B, et al., “Acute bronchospasm due to exposure topolymethylmethacrylate vapors during percutaneous vertebroplasty”, Am.J. Roentgenol. 2003; 180:543-544.

In both higher pressure cement injection (vertebroplasty) andballoon-tamped cementing procedures (kyphoplasty), the methods do notprovide for well controlled augmentation of vertebral body height. Thedirect injection of bone cement simply follows the path of leastresistance within the fractured bone. The expansion of a balloon appliesalso compacting forces along lines of least resistance in the collapsedcancellous bone. Thus, the reduction of a vertebral compression fractureis not optimized or controlled in high pressure balloons as forces ofballoon expansion occur in multiple directions.

In a kyphoplasty procedure, the physician often uses very high pressures(e.g., up to 200 or 300 psi) to inflate the balloon which crushes andcompacts cancellous bone. Expansion of the balloon under high pressuresclose to cortical bone can fracture the cortical bone, typically theendplates, which can cause regional damage to the cortical bone with therisk of cortical bone necrosis. Such cortical bone damage is highlyundesirable as the endplate and adjacent structures provide nutrientsfor the disc.

Kyphoplasty also does not provide a distraction mechanism capable of100% vertebral height restoration. Further, the kyphoplasty balloonsunder very high pressure typically apply forces to vertebral endplateswithin a central region of the cortical bone that may be weak, ratherthan distributing forces over the endplate.

There is a general need to provide systems and methods for use intreatment of vertebral compression fractures that provide a greaterdegree of control over introduction of bone support material, and thatprovide better outcomes. The present invention meets this need andprovides several other advantages in a novel and nonobvious manner.

SUMMARY OF THE INVENTION

Certain embodiments of the invention provide systems and methods forutilizing Rf energy in combination with a bone fill material thatcarries an electrically conductive filler for polymerizing surfaceportions of the inflow plume to thereby control the direction of flowand the ultimate geometry of a flowable, in-situ hardenable composite.The system and method can further include means for sealing tissue inthe interior of a vertebra to prevent migration of monomers, fat oremboli into the patient's bloodstream.

In some embodiments, a method for treating a vertebral fracture cancomprise controllably applying energy from an energy source to a bonecement in an injector system via a heating element disposed in theinjector system, at least a portion of the injector system having anoutlet port positionable within cancellous bone, the applied energy canselectively increase the viscosity of the bone cement. The method canalso comprise injecting a volume of bone cement having the selectivelyincreased viscosity into the cancellous bone and controlling theviscosity of the cement injected through the injector system via thecontrolled application of energy. In some embodiments this is done sothat the bone cement flows into cancellous bone along a flow pathbetween the outlet port and a periphery of the volume, and so at least aportion of the flow path comprises bone cement interdigitated with thecancellous bone.

A method for treating a vertebral body, according to some embodimentscan comprise controllably applying energy from an energy source to abone cement wherein the application of energy selectively increases theviscosity of the bone cement and injecting a volume of the bone cementhaving the selectively increased viscosity into cancellous bone of thevertebral body. The viscosity of the volume of bone cement can becontrolled by the controlled application of energy. The injected volumeof bone cement can flow along a flow path that interdigitates andpermeates the cancellous bone and the volume of bone cement can beinjected without previously compacting the cancellous bone.

An additional embodiment of a method for treating a vertebral body cancomprise controllably applying energy from an energy source to a bonecement via a heating element in an injector system, the applied energyselectively increasing viscosity of the bone cement; and injecting avolume of the bone cement through an outlet port of the injector systeminto cancellous bone of the vertebral body wherein the viscosity of thevolume of bone cement is controlled by the controlled application ofenergy. The injected volume of the bone cement can flow along a flowpath interdigitating and permeating the cancellous bone, an outer regionof the flow path can surround interdigitated cancellous bone located inthe flow path between the outer region and the outlet port.

In accordance with another embodiment, a method for treating bone isprovided comprising introducing at least one instrument working end intoan interior region of a bone member. The method can also compriseintroducing an infill material into the interior region of the bonemember and applying energy from an energy source through the at leastone working end to the fill material.

These and other objects of the present invention will become readilyapparent upon further review of the following drawings andspecification.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the invention and to see how it may becarried out in practice, some preferred embodiments are next described,by way of non-limiting examples only, with reference to the accompanyingdrawings, in which like reference characters denote correspondingfeatures consistently throughout similar embodiments in the attacheddrawings.

FIG. 1 is a schematic side view of a spine segment showing a vertebrawith a compression fracture and an introducer, in accordance with oneembodiment disclosed herein.

FIG. 2A is a schematic perspective view of a system for treating bone,in accordance with one embodiment.

FIG. 2B is a schematic perspective sectional view of a working end ofthe introducer taken along line 2B-2B of FIG. 2A.

FIG. 3A is a schematic perspective view of a working end of a probe, inaccordance with one embodiment.

FIG. 3B is a schematic perspective view of a working end of a probe, inaccordance with another embodiment.

FIG. 3C is a schematic perspective view of a working end of a probe, inaccordance with yet another embodiment.

FIG. 4 is a schematic sectional side view of one embodiment of a workingend of a probe, in accordance with one embodiment.

FIG. 5A is a schematic side view of a probe inserted into a vertebralbody and injecting flowable fill material into the vertebral body.

FIG. 5B is a schematic side view of the probe in FIG. 5A injecting arelatively high viscosity volume of flowable fill material into thevertebral body, in accordance with one embodiment of the presentinvention.

FIG. 6 is a schematic perspective view of a system for treating bone, inaccordance with another embodiment.

FIG. 7A is a schematic sectional view of a fill material, in accordancewith one embodiment.

FIG. 7B is a schematic sectional view of a fill material, in accordancewith another embodiment.

FIG. 8A is a schematic perspective view of a system for treating bone,in accordance with another embodiment.

FIG. 8B is a schematic perspective view of the system in FIG. 8A,injecting an additional volume of fill material into a vertebral body.

FIG. 9A is a schematic sectional view of one step in a method fortreating bone, in accordance with one embodiment.

FIG. 9B is a schematic sectional view of another step in a method fortreating bone, in accordance with one embodiment.

FIG. 9C is a schematic sectional view of still another step in a methodfor treating bone, in accordance with one embodiment.

FIG. 10A is a schematic sectional view of a step in a method fortreating bone, in accordance with another embodiment.

FIG. 10B is a schematic sectional view of another step in a method fortreating bone, in accordance with another embodiment.

FIG. 11A is a schematic perspective view of a system for treating bone,in accordance with another embodiment.

FIG. 11B is a schematic perspective view of the system in FIG. 11A,applying energy to a fill material.

FIG. 12 is a schematic perspective view of a system for treating bone,in accordance with another embodiment.

FIG. 13A is a side view of a working end of an introducer, in accordancewith one embodiment.

FIG. 13B is a side view of a working end of an introducer, in accordancewith another embodiment.

FIG. 13C is a side view of a working end of an introducer, in accordancewith yet another embodiment.

FIG. 13D is a side view of a working end of an introducer, in accordancewith still another embodiment.

FIG. 14 is a perspective view of a system for treating bone, inaccordance with another embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates one embodiment of the invention in treating a spinesegment in which a vertebral body 90 has a wedge compression fractureindicated at 94. In one embodiment, the systems and methods of theinvention are directed to safely introducing a bone fill material intocancellous bone of the vertebra without extravasation of fill materialin unwanted directions (i) to prevent micromotion in the fracture foreliminating pain, and (ii) to support the vertebra and increasevertebral body height. Further, the invention includes systems andmethods for sealing cancellous bone (e.g., blood vessels, fatty tissuesetc.) in order to prevent monomers, fat, fill material and other embolifrom entering the venous system during treatment.

FIG. 1 illustrates a fractured vertebra and bone infill system 100 whichincludes a probe 105 having a handle end 106 extending to an elongatedintroducer 110A and a working end 115A, shown in FIG. 2A. The introduceris shown introduced through pedicle 118 of the vertebra for accessingthe osteoporotic cancellous bone 122 (See FIG. 2A). The initial aspectsof the procedure are similar to conventional percutaneous vertebroplastywherein the patient is placed in a prone position on an operating table.The patient is typically under conscious sedation, although generalanesthesia is an alternative. The physician injects a local anesthetic(e.g., 1% Lidocaine) into the region overlying the targeted pedicle orpedicles as well as the periosteum of the pedicle(s). Thereafter; thephysician uses a scalpel to make a 1 to 5 mm skin incision over eachtargeted pedicle. Thereafter, the introducer 110A is advanced throughthe pedicle into the anterior region of the vertebral body, whichtypically is the region of greatest compression and fracture. Thephysician confirms the introducer path posterior to the pedicle, throughthe pedicle and within the vertebral body by anteroposterior and lateralX-Ray projection fluoroscopic views. The introduction of infill materialas described below can be imaged several times, or continuously, duringthe treatment depending on the imaging method.

It should be appreciated that the introducer 110A also can be introducedinto the vertebra from other angles, for example, along axis 113 throughthe wall of the vertebral body 114 as in FIG. 1 or in an anteriorapproach (not shown). Further, first and second cooperating introducerscan be used in a bilateral transpedicular approach. Additionally, anymechanism known in the art for creating an access opening into theinterior of the vertebral body 90 can be used, including open surgicalprocedures.

DEFINITIONS

“Bone fill material, infill material or composition” includes itsordinary meaning and is defined as any material for infilling a bonethat includes an in-situ hardenable material. The fill material also caninclude other “fillers” such as filaments, microspheres, powders,granular elements, flakes, chips, tubules and the like, autograft orallograft materials, as well as other chemicals, pharmacological agentsor other bioactive agents.

“Flowable material” includes its ordinary meaning and is defined as amaterial continuum that is unable to withstand a static shear stress andresponds with an irrecoverable flow (a fluid)—unlike an elastic materialor elastomer that responds to shear stress with a recoverabledeformation. Flowable material includes fill material or composites thatinclude a fluid (first) component and an elastic or inelastic material(second) component that responds to stress with a flow, no matter theproportions of the first and second component, and wherein the aboveshear test does not apply to the second component alone.

An “elastomer” includes its ordinary meaning and is defined as materialhaving to some extent the elastic properties of natural rubber whereinthe material resumes or moves toward an original shape when a deformingforce is removed.

“Substantially” or “substantial” mean largely but not entirely. Forexample, substantially may mean about 10% to about 99.999%, about 25% toabout 99.999% or about 50% to about 99.999%.

“Osteoplasty” includes its ordinary meaning and means any procedurewherein fill material is delivered into the interior of a bone.

“Vertebroplasty” includes its ordinary meaning and means any procedurewherein fill material is delivered into the interior of a vertebra.

Now referring to FIGS. 2A and 2B, the end of introducer 110A is shownschematically after being introduced into cancellous bone 122 with aninflow of fill material indicated at 120. The cancellous bone can be inany bone, for example in a vertebra. It can be seen that the introducer110A and working end 115A comprise a sleeve or shaft that is preferablyfabricated of a metal having a flow channel 118 extending therethroughfrom the proximal handle end 106 (see FIG. 1). In one embodiment, theintroducer shaft is a stainless steel tube 123 having an outsidediameter ranging between about 3.5 and 4.5 mm, but other dimensions arepossible. As can be seen in FIGS. 2A and 3A, the flow channel 118 canterminate in a single distal open termination or outlet 124 a in theworking end 115A, or there can be a plurality of flow outlets or ports124 b configured angularly about the radially outward surfaces of theworking end 115A of FIG. 3B. The outlets in the working end thus allowfor distal or radial ejection of fill material, or a working end canhave a combination of radial and distal end outlets. As can be seen inFIG. 3C, the distal end of working end 115A also can provide an angleddistal end outlet 124 c for directing the flow of fill material from theoutlet by rotating the working end.

In FIGS. 2A and 2B, it can be seen that system 100 includes a remoteenergy source 125A and controller 125B that are operatively coupled toan energy emitter 128 in working end 115A for applying energy to fillmaterial 120 contemporaneous with and subsequent to ejection of the fillmaterial from the working end. As shown in FIG. 2A, a preferred energysource 125A is a radiofrequency (Rf) source known in the art that isconnected to at least one electrode (132 a and 132 b in FIGS. 2A and 2B)in contact with injected fill material 120 that carries a radiosensitivecomposition therein. It is equally possible to use other remote energysources and emitters 128 in the working end which fall within the scopeof the invention, such as (i) an electrical source coupled to aresistive heating element in the working end, (ii) a light energy source(coherent or broadband) coupled to an optical fiber or other lightchannel terminating in the working end; (iii) an ultrasound sourcecoupled to an emitter in the working end; or (iv) a microwave sourcecoupled to an antenna in the working end. In still another embodiment,the energy source can be a magnetic source. The fill material isconfigured with an energy-absorbing material or an energy-transmittingmaterial that cooperates with energy delivery from a selected energysource. For example, the energy-absorbing or energy-transmittingmaterial can be a radiosensitive or conductive material for cooperatingwith an Rf source, chromophores for cooperating with a light source,ferromagnetic particles for cooperating with a magnetic source, and thelike.

As can be understood from FIGS. 2A and 2B, the exemplary introducer 110Ais operatively coupleable to a source 145 of bone fill material 120together with a pressure source or mechanism 150 that operates on thesource of fill material to deliver the fill material 120 through theintroducer 110A into a bone (see arrows). The pressure source 150 cancomprise any type of pump mechanism, such as a piston pump or screwpump. In FIG. 2B, the pump mechanism is shown as a piston or plunger 152that is slideable in channel 118 of introducer 110A.

As shown in FIGS. 2A and 2B, the introducer 110A preferably has anelectrically and thermally insulative interior sleeve 154 that definesinterior flow channel 118. The sleeve can be any suitable polymer knownin the art such as PEEK, Teflon™ or a polyimide. As can be seen in FIG.2B, interior sleeve 154 carries conductive surfaces that function asenergy emitter 128, and more particularly comprise spaced apart opposingpolarity electrodes 132 a and 132 b. The electrodes 132 a and 132 b canhave any spaced apart configuration and are disposed about the distaltermination of channel 118 or about the surfaces of outlet 124 a. Theelectrode configuration alternatively can include a first electrode inthe interior of channel 118 and a second electrode on an exterior ofintroducer 110A. For example, the metallic sleeve 123 or a distalportion thereof can comprise one electrode. In a preferred embodiment,the electrodes 132 a and 132 b are connected to Rf energy source 125Aand controller 125B by electrical cable 156 with (+) and (−) electricalleads 158 a and 158 b therein that extend through the insulative sleeve154 to the opposing polarity electrodes. In one embodiment, theelectrical cable 156 is detachably coupled to the handle end 106 ofprobe 105 by male-female plug (not shown). The electrodes 132 a and 132b can be fabricated of any suitable materials known to those skilled inthe art, such as stainless steels, nickel-titanium alloys and alloys ofgold, silver platinum and the like.

In one embodiment, not shown, the working end 115A can also carry anysuitable thermocouple or temperature sensor for providing data tocontroller 125B relating to the temperature of the fill material 120during energy delivery. One or more thermocouples may be positioned atthe distal tip of the introducer, or along an outer surface of theintroducer and spaced from the distal end, in order to providetemperature readings at different locations within the bone. Thethermocouple may also be slideable along the length of the introducer.In another embodiment, the working end can have at least one side port(not shown) in communication with a coolant source, the port configuredto provide the coolant (e.g., saline) therethrough into the cancellousbone 122 to cool the cancellous bone in response to a temperaturereading from the temperature sensor.

Now turning to FIG. 4, the sectional view of working end 115Aillustrates the application of energy to fill material 120 as it isbeing ejected from outlet 124 a. The fill material 120 in the proximalportion of channel 118 can be a low viscosity flowable material such asa two-part curable polymer that has been mixed (e.g., PMMA) but withoutany polymerization, for example, having a viscosity of less than about50,000 cps. Such a low viscosity fill material allows for simplifiedlower pressure injection through introducer 110A. Further, the systemallows the use of a low viscosity fill material 120 which can save agreat deal of time for the physician.

In a preferred embodiment, it is no longer necessary to wait for thebone cement to partly polymerize before injection. As depicted in FIG.4, energy delivery at selected parameters from electrodes 132 a and 132b to fill material 120 contemporaneous with its ejection from outlet 124a selectively alters a property of fill material indicated at 120′. Inone embodiment, the altered flow property is viscosity. For example, theviscosity of the fill material 120′ can be increased to a higherviscosity ranging from about 100,000 cps or more, 1,000,000 cps or more,to 2,000,000 cps or more. In another embodiment, the flow property isYoung's modulus. For example, the Young's modulus of the fill material120′ can be altered to be between about 10 kPa and about 10 GPa. Instill another embodiment, the flow property can be one of durometer,hardness and compliance.

Preferably, the fill material carries a radiosensitive composition forcooperating with the Rf source 125A, as further described below. At apredetermined fill material flow rate and at selected Rf energy deliveryparameters, the altered fill material 120′ after ejection can comprisean elastomer. At yet another predetermined fill material flow rate andat other Rf energy delivery parameters, the altered fill material 120′after ejection can comprise a substantially solid material. In thesystem embodiment utilized for vertebroplasty as depicted in FIGS. 2Aand 5B, the controller is adapted for delivering Rf energycontemporaneous with the selected flow rate of fill material to providea substantially high viscosity fill material that is still capable ofpermeating cancellous bone. In other osteoplasty procedures such astreating necrosis of a bone, the system controller 125B can be adaptedto provide much harder fill material 120′ upon ejection from outlet 124a. Further, the system can be adapted to apply Rf energy to the fillmaterial continuously, or in a pulse mode or in any selected intervalsbased on flow rate, presets, or in response to feedback from temperaturesensors, impedance measurements or other suitable signals known to thoseskilled in the art.

FIGS. 5A and 5B are views of a vertebra 90 that are useful forexplaining relevant aspects of one embodiment of the invention whereinworking end 110A is advanced into the region of fracture 94 incancellous bone 122. FIG. 5A indicates system 100 being used to injectflow material 120 into the vertebra with the flow material having aviscosity similar to conventional vertebroplasty or kyphoplasty, forexample having the consistency of toothpaste. FIG. 5A depicts thesituation wherein high pressure injection of a low viscosity materialcan simply follow paths of least resistance along a recent fractureplane 160 to migrate anteriorly in an uncontrolled manner. The migrationof fill material could be any direction, including posteriorly towardthe spinal canal or into the disc space depending on the nature of thefracture.

FIG. 5B illustrates system 100 including actuation of Rf source 125A bycontroller 125B to contemporaneously heat the fill material to ejectaltered fill material 120′ with a selected higher viscosity intocancellous bone 122, such as the viscosities described above. With aselected higher viscosity, FIG. 5B depicts the ability of the system toprevent extravasation of fill material and to controllably permeate andinterdigitate with cancellous bone 122, rather than displacingcancellous bone, with a plume 165 that engages cortical bone vertebralendplates 166 a and 166 b. The fill material broadly engages surfaces ofthe cortical endplates to distribute pressures over the endplates. In apreferred embodiment, the fill material controllably permeatescancellous bone 122 and is ejected at a viscosity adequate tointerdigitate with the cancellous bone 122. Fill material with aviscosity in the range of about 100,000 cps to 2,000,000 cps may beejected, though even lower or higher viscosities may also be sufficient.The Rf source may selectively increase the viscosity of the fillmaterial by about 10% or more as it is ejected from the introducer 115A.In other embodiments, the viscosity may be increased by about 20%, 50%,100%, 500% or 1000% or more.

Still referring to FIG. 5B, it can be understood that continued inflowsof high viscosity fill material 120′ and the resultant expansion ofplume 165 will apply forces on endplates 166 a and 166 b to at leastpartially restore vertebral height. It should be appreciated that theworking end 115A can be translated axially between about the anteriorthird of the vertebral body and the posterior third of the vertebralbody during the injection of fill material 120′, as well as rotating theworking end 115A which can be any of the types described above (FIGS.3A-3C).

FIG. 6 is a schematic view of an alternative embodiment of system 100wherein Rf source 125A and controller 125B are configured to multiplexenergy delivery to provide additional functionality. In one mode ofoperation, the system functions as described above and depicted in FIGS.4 and 5B to alter flow properties of flowable fill material 120′ as itis ejected from working end 115A. As can be seen in FIG. 6, the systemfurther includes a return electrode or ground pad indicated at 170. Thusthe system can be operated in a second mode of operation whereinelectrodes 132 a and 132 b are switched to a common polarity (or thedistal portion of sleeve 123 can comprise such an electrode) to functionin a mono-polar manner in conjunction with ground pad 170. This secondmode of operation advantageously creates high energy densities about thesurface of plume 165 to thereby ohmically heat tissue at the interfaceof the plume 165 and the body structure.

In FIG. 6, the ohmically heated tissue is indicated at 172, wherein thetissue effect is coagulation of blood vessels, shrinkage of collagenoustissue and generally the sealing and ablation of bone marrow,vasculature and fat within the cancellous bone. The Rf energy levels canbe set at a sufficiently high level to coagulate, seal or ablate tissue,with the controller delivering power based, for example, on impedancefeedback which will vary with the surface area of plume 165. Ofparticular interest, the surface of plume 165 is used as an electrodewith an expanding wavefront within cancellous bone 122. Thus, thevasculature within the vertebral body can be sealed by controlled ohmicheating at the same time that fill material 120′ is permeating thecancellous bone. Within the vertebral body are the basivertebral(intravertebral) veins which are paired valveless veins connecting withnumerous venous channels within the vertebra (pars spongiosa/red bonemarrow). These basivertebral veins drain directly into the externalvertebral venous plexus (EVVP) and the superior and inferior vena cava.The sealing of vasculature and the basivertebral veins is particularlyimportant since bone cement and monomer embolism has been frequentlyobserved in vertebroplasty and kyphoplasty cases (see “Anatomical andPathological Considerations in Percutaneous Vertebroplasty andKyphoplasty: A Reappraisal of the Vertebral Venous System”, Groen, R. etal, Spine Vol. 29, No. 13, pp 1465-1471 2004). It can be thus understoodthat the method of using the system 100 creates and expands a“wavefront” of coagulum that expands as the plume 165 of fill materialexpands. The expandable coagulum layer 172, besides sealing the tissuefrom emboli, contains and distributes pressures of the volume of infillmaterial 120′ about the plume surface.

The method depicted in FIG. 6 provides an effective means for sealingtissue via ohmic (Joule) heating. It has been found that passive heattransfer from the exothermic reaction of a bone cement does notadequately heat tissue to the needed depth or temperature to sealintravertebral vasculature. In use, the mode of operation of the system100 in a mono-polar manner for ohmically heating and sealing tissue canbe performed in selected intervals alone or in combination with thebi-polar mode of operation for controlling the viscosity of the injectedfill material.

In general, one aspect of the vertebroplasty or osteoplasty method inaccordance with one of the embodiments disclosed herein allows forin-situ control of flows of a flowable fill material, and moreparticularly comprises introducing a working end of an introducer sleeveinto cancellous bone, ejecting a volume of flowable fill material havinga selected viscosity and contemporaneously applying energy (e.g., Rfenergy) to the fill material from an external source to thereby increasethe viscosity of at least portion of the volume to prevent fillextravasation. In a preferred embodiment, the system increases theviscosity by about 20% or more. In another preferred embodiment, thesystem increases the viscosity by about 50% or more.

In another aspect of one embodiment of a vertebroplasty method, thesystem 100 provides means for ohmically heating a body structure aboutthe surface of the expanding plume 165 of fill material to effectivelyseal intravertebral vasculature to prevent emboli from entering thevenous system. The method further provides an expandable layer ofcoagulum about the infill material to contain inflow pressures anddistribute further expansion forces over the vertebral endplates. In apreferred embodiment, the coagulum expands together with at least aportion of the infill material to engage and apply forces to endplatesof the vertebra.

Of particular interest, one embodiment of fill material 120 as used inthe systems described herein (see FIGS. 2A, 4, 5A-5B and 6) is acomposite comprising an in-situ hardenable or polymerizable cementcomponent 174 and an electrically conductive filler component 175 in asufficient volume to enable the composite to function as a dispersableelectrode (FIG. 6). In one type of composite, the conductive fillercomponent is any biocompatible conductive metal. In another type ofcomposite, the conductive filler component is a form of carbon. Thebiocompatible metal can include at least one of titanium, tantalum,stainless steel, silver, gold, platinum, nickel, tin, nickel titaniumalloy, palladium, magnesium, iron, molybdenum, tungsten, zirconium,zinc, cobalt or chromium and alloys thereof. The conductive fillercomponent has the form of at least one of filaments, particles,microspheres, spheres, powders, grains, flakes, granules, crystals,rods, tubules and the like. Such conductive filler components can be atleast one of solid, porous or hollow, with conductive filaments 176 aillustrated in FIG. 7A and conductive particles 176 b depicted in FIG.7B.

In a preferred embodiment, the conductive filler comprises choppedmicrofilaments or ribbons of a metal as in FIG. 7A that have across-section dimension across a major axis ranging between about0.0005″ and 0.01″. The lengths of the microfilaments or ribbons rangefrom about 0.01″ to 0.50″. The microfilaments or ribbons are ofstainless steel or titanium and are optionally coated with a thin goldlayer or silver layer that can be deposited by electroless platingmethods. Of particular interest, the fill material 120 of FIG. 7A has anin situ hardenable cement component 174 than has a first low viscosityand the addition of the elongated microfilament conductive fillercomponent 175 causes the composite 120 to have a substantially highapparent viscosity due to the high surface area of the microfilamentsand its interaction with the cement component 174.

In another embodiment of bone fill material 120, the conductive fillercomponent comprises elements that have a non-conductive core portionwith a conductive cladding portion for providing electrosurgicalfunctionality. The non-conductive core portions are selected from thegroup consisting of glass, ceramic or polymer materials. The claddingcan be any suitable conductive metal as described above that can bedeposited by electroless plating methods.

In any embodiment of bone fill material that uses particles,microspheres, spheres, powders, grains, flakes, granules, crystals orthe like, such elements can have a mean dimension across a principalaxis ranging from about 0.5 micron to 2000 microns. More preferably, themean dimension across a principal axis range from about 50 microns to1000 microns. It has been found that metal microspheres having adiameter of about 800 microns are useful for creating conductive bonecement that can function as an electrode.

In one embodiment, a conductive filler comprising elongatedmicrofilaments wherein the fill material has from about 0.5% to 20%microfilaments by weight. More preferably, the filaments are from about1.0% to 10% by weight of the fill material. In other embodiments whereinthe conductive filler comprises particles or spheres, the conductivefiller can comprise from about 5% of the total weight to about 80% ofthe weight of the material.

In an exemplary fill material 120, the hardenable component can be anyin-situ hardenable composition such as at least one of PMMA, monocalciumphosphate, tricalcium phosphate, calcium carbonate, calcium sulfate orhydroxyapatite.

Referring now to FIGS. 8A and 8B, an alternative method is shown whereinthe system 100 and method are configured for creating asymmetries inproperties of the infill material and thereby in the application offorces in a vertebroplasty. In FIG. 8A, the pressure mechanism 150 isactuated to cause injection of an initial volume or aliquot of fillmaterial 120′ that typically is altered in viscosity in working end 110Aas described above—but the method encompasses flows of fill materialhaving any suitable viscosity. The fill material is depicted in FIGS. 8Aand 8B as being delivered in a unilateral transpedicular approach, butany extrapedicular posterior approach is possible as well as anybilateral posterior approach. The system in FIGS. 8A-8B againillustrates a vertical plane through the fill material 120′ that flowsunder pressure into cancellous bone 122 with expanding plume orperiphery indicated at 165. The plume 165 has a three dimensionalconfiguration as can be seen in FIG. 8B, wherein the pressurized flowmay first tend to flow more horizontally that vertically. One embodimentof the method of the invention includes the physician translating theworking end slightly and/or rotating the working end so that flowoutlets 124 a are provided in a selected radial orientation. In apreferred embodiment, the physician intermittently monitors the flowsunder fluoroscopic imaging as described above.

FIG. 8B depicts a contemporaneous or subsequent energy-delivery step ofthe method wherein the physician actuates Rf electrical source 125A andcontroller 125B to cause Rf current delivery from at least one electrodeemitter 128 to cause ohmic (Joule) heating of tissue as well as internalheating of the inflowing fill material 120′. In this embodiment, theexterior surface of sleeve 123 is indicated as electrode or emitter 128with the proximal portion of introducer 110A having an insulator coating178. The Rf energy is preferably applied in an amount and for a durationthat coagulates tissue as well as alters a flowability property ofsurface portions 180 of the initial volume of fill material proximatethe highest energy densities in tissue.

In one preferred embodiment, the fill material 120 is particularlydesigned to create a gradient in the distribution of conductive fillerwith an increase in volume of material injected under high pressure intocancellous bone 122. This aspect of the method in turn can be usedadvantageously to create asymmetric internal heating of the fill volume.In this embodiment, the fill material 120 includes a conductive fillerof elongated conductive microfilaments 176 a (FIG. 7A). The filamentsare from about 2.0% to 5% by weight of the fill material, with thefilaments having a diameter ranging between 0.001″ and 0.010″ and alength ranging from 1.0 mm to 5.0 mm. It has been found that elongatedconductive microfilaments 176 a result in resistance to flows thereaboutwhich causes such microfilaments to aggregate away from the most activemedia flows that are concentrated in the center of the vertebraproximate to outlet 124 a. Thus, the conductive microfilaments 176 aattain a higher concentration in the peripheral or surface portion 180of the plume which in turn will result in greater internal heating ofthe fill portions having such higher concentrations of conductivefilaments. The active flows also are controlled by rotation ofintroducer 110A to eject the material preferentially, for examplelaterally as depicted in FIGS. 8A and 8B rather that vertically. Thehandle 106 of the probe 105 preferably has markings to indicate therotational orientation of the outlets 124 b.

FIG. 8A depicts the application of Rf energy in a monopolar mannerbetween electrode emitter 128 and ground pad 170, which thus causesasymmetric heating wherein surface portion 180 heating results ingreater polymerization therein. As can be seen in FIG. 8A, the volume offill material thus exhibits a gradient in a flowability property, forexample with surface region 180 having a higher viscosity than inflowingmaterial 120′ as it is ejected from outlet 124 a. In one embodiment, thegradient is continuous. Such heating at the plume periphery 165 cancreate an altered, highly viscous surface region 180. This step of themethod can transform the fill material to have a gradient in flowabilityin an interval of about 5 seconds to 500 seconds with surface portion180 being either a highly viscous, flowable layer or an elastomer thatis expandable. In preferred embodiments, the interval of energy deliveryrequired less than about 120 seconds to alter fill material to aselected asymmetric condition. In another aspect of the invention, theRf energy application for creating the gradient in flowability also canbe optimized for coagulating and sealing adjacent tissue.

The combination of the viscous surface portion 180 and the tissuecoagulum 172 may function as an in-situ created stretchable, butsubstantially flow-impervious, layer to contain subsequent high pressureinflows of fill material. Thus, the next step of the method of theinvention is depicted in FIG. 8B which includes injecting additionalfill material 120′ under high pressure into the interior of the initialvolume of fill material 120 that then has a highly viscous, expandablesurface. The viscous, expandable surface desirably surrounds cancellousbone. By this means, the subsequent injection of fill material canexpand the fill volume to apply retraction forces on the vertebraendplates 166 a and 166 b to provide vertical jacking forces,distracting cortical bone, for restoring vertebral height, as indicatedby the arrows in FIG. 8B. The system can generate forces capable ofbreaking callus in cortical bone about a vertebral compression fracturewhen the fracture is less than completely healed.

In one embodiment, the method includes applying Rf energy to createhighly viscous regions in a volume of fill material and thereafterinjecting additional fill material 120 to controllably expand the fillvolume and control the direction of force application. The scope of themethod further includes applying Rf energy in multiple intervals orcontemporaneous with a continuous flow of fill material. The scope ofthe method also includes applying Rf in conjunction with imaging meansto prevent unwanted flows of the fill material. The scope of theinvention also includes applying Rf energy to polymerize and acceleratehardening of the entire fill volume after the desired amount of fillmaterial has been injected into a bone.

In another embodiment, the method includes creating Rf current densitiesin selected portions of the volume of fill material 120 to createasymmetric fill properties based on particular characteristics of thevertebral body. For example, the impedance variances in cancellous boneand cortical bone can be used to create varied Rf energy densities infill material 120 to create asymmetric properties therein. Continuedinjection of fill material 120 are thus induced to apply asymmetricretraction forces against cortical endplates 166 a and 166 b, whereinthe flow direction is toward movement or deformation of the lowerviscosity portions and away from the higher viscosity portions. In FIGS.9A-9C, it can be seen that in a vertebroplasty, the application of Rfenergy in a mono-polar manner as in FIG. 6 naturally and preferentiallycreates more highly viscous, deeper “altered” properties in surfaces ofthe lateral peripheral fill volumes indicated at 185 and 185′ and lessviscous, thinner altered surfaces in the superior and inferior regions186 and 186′ of fill material 120. This effect occurs since Rf currentdensity is localized about paths of least resistance which arepredominantly in locations proximate to highly conductive cancellousbone 122 a and 122 b. The Rf current density is less in locationsproximate to less conductive cortical bone indicated at 166 a and 166 b.Thus, it can be seen in FIG. 9B that the lateral peripheral portions 185and 185′ of the first flows of fill material 120 are more viscous andresistant to flow and expansion than the thinner superior and inferiorregions. In FIG. 9C, the asymmetrical properties of the initial flows offill material 120 allows the continued flows to apply retraction forcesin substantially vertical directions to reduce the vertebral fractureand increase vertebral height, for example from VH (FIG. 9B) to VH′ inFIG. 9C.

FIGS. 10A and 10B are schematic views that further depict a methodcorresponding to FIGS. 9B and 9C that comprises expanding cancellousbone for applying retraction forces against cortical bone, e.g.,endplates of a vertebra in a vertebroplasty. As can be seen in FIG. 10A,an initial volume of flowable fill material 120 is injected intocancellous bone wherein surface region 180 is altered as described aboveto be highly viscous or to comprise and elastomer that is substantiallyimpermeable to interior flows but still be expandable. The surfaceregion 180 surrounds subsequent flows of fill material 120′ whichinterdigitate with cancellous bone. Thereafter, as shown in FIG. 10B,continued high pressure inflow into the interior of the fill materialthereby expands the cancellous bone 122 together with the interdigitatedfill material 120′. As can be seen in FIG. 10B, the expansion ofcancellous bone 122 and fill material 120′ thus applies retractionforces to move cortical bone endplates 166 a and 166 b. The method ofexpanding cancellous bone can be used to reduce a bone fracture such asa vertebral compression fracture and can augment or restore the heightof a fractured vertebra. The system thus can be used to support retractand support cortical bone, and cancellous bone. The method can alsorestore the shape of an abnormal vertebra, such as one damaged by atumor.

After utilizing system 100 to introduce, alter and optionally hardenfill material 120 as depicted in FIGS. 9A-9C and 10A-10B, the introducer110A can be withdrawn from the bone. Alternatively, the introducer 110Acan have a release or detachment structure indicated at 190 forde-mating the working end from the proximal introducer portion asdescribed in co-pending U.S. patent application Ser. No. 11/130,843,filed May 16, 2005, the entirety of which is hereby incorporated byreference.

Another system embodiment 200 for controlling flow directions and forcreating asymmetric properties is shown in FIGS. 11A and 11B, whereinfirst and second introducers 110A and 110B similar to those describedabove are used to introduce first and second independent volumes 202 aand 202 b of fill material 120 in a bilateral approach. In thisembodiment, the two fill volumes function as opposing polarityelectrodes in contact with electrodes 205 a and 205 b of the workingends. Current flow between the electrodes thus operates in a bi-polarmanner with the positive and negative polarities indicated by the (+)and (−) symbols. In this method, it also can be seen that the highestcurrent density occurs in the three dimensional surfaces of volumes 202a and 202 b that face one another. This results in creating thethickest, high viscosity surfaces 208 in the medial, anterior andposterior regions and the least “altered” surfaces in the laterallyoutward regions. This method is well suited for preventing posterior andanterior flows and directing retraction forces superiorly and inferiorlysince lateral flow are contained by the cortical bone at lateral aspectsof the vertebra. The system can further be adapted to switch ohmicheating effects between the bi-polar manner and the mono-polar mannerdescribed previously.

Now referring to FIG. 12, another embodiment is shown wherein atranslatable member 210 that functions as an electrode is carried byintroducer 110A. In a preferred embodiment, the member 210 is asuperelastic nickel titanium shape memory wire that has a curved memoryshape. The member 210 can have a bare electrode tip 212 with aradiopaque marking and is otherwise covered by a thin insulator coating.In FIG. 12, it can be seen that the introducer can be rotated and themember can be advanced from a port 214 in the working end 115A underimaging. By moving the electrode tip 212 to a desired location and thenactuating RF current, it is possible to create a local viscous orhardened region 216 of fill material 120. For example, if imagingindicates that fill material 120 is flowing in an undesired direction,then injection can be stopped and Rf energy can be applied to harden theselected location.

In another embodiment similar to the one shown in FIG. 12, thetranslatable member 210 can comprise a hollow needle that injects achemical agent (e.g., a catalyst) to accelerate local curing of the fillmaterial 120. Alternatively, the hollow needle can deliver amicroencapsulated chemical agent that is released by Rf energy deliveryto sacrifice the microcapsule.

FIGS. 13A-13D illustrate other embodiments of the introducer 110A, whichinclude structures for engaging the working end 115A in bone tosubstantially prevent it from moving proximally when very high pressuresare used to inject bone fill material 120, for example to augmentvertebral height when treating a VCF. FIG. 13A illustrates a working endwith threads 220 for helically advancing the introducer which willsecure the introducer in bone. FIG. 13B illustrates a working end withfirst and second concentric sleeves 222 a and 222 b that can be used tobuckle and radially expand a resilient element 224 such as a rubbermember. Alternatively, the system of FIG. 13B could be configured tobuckle at least one metal element. FIG. 13C illustrates a working endwith barbs 225 that engage the bone as the structure is movedproximally. In the illustrated embodiment, such a working end can bedetached using a detachment mechanism indicated at 190 as describedabove. In another embodiment, the introducer barbs 225 can be configuredto collapse somewhat under rotation to thereby rotate and withdraw theintroducer from bone. FIG. 13D illustrates a working end with anexpandable balloon structure 226 for gripping bone that is inflatedthrough lumen 228 from an inflation source.

FIG. 14 illustrates another embodiment of the invention wherein theon-demand hardenable fill material 120 is combined with an implant 300such as a bone screw, pin, shaft, joint reconstruction body or the like.As one example of an implant, FIG. 14 illustrates a metal bone screw 302that cooperates with driver member 305 for helically driving the screw.The bone screw 302 has a lumen 308 that communicates with a plurality ofoutlets 310 in the implant body. In one embodiment, the driver 305 has acooperating bore 312 that is coupled to a source 145 of conductive fillmaterial 120 as described above. Further, the system includes Rf source125A and controller 125B for applying Rf energy to harden the fillmaterial on demand. In one embodiment, the Rf source is coupled to theelectrically conductive driver 305 which carries Rf current to the bonescrew by contact. As can be seen in FIG. 14, the method of the inventionincludes driving the bone screw in a bone, and then injecting the fillmaterial 120 which will flow through outlets 310 (see arrows) in theimplant. Thereafter, the Rf source is actuated to cure the fill material120 to thereby fix the implant in bone.

It should be appreciated that the system FIG. 14 can be coupled with anytype of bone implant, including joint reconstruction components forhips, knees, shoulders and the like, ligament or tendon implants thatare fixed in a bore in bone, reconstructive surgery implants, and anyother screw, pin or plate or the like.

The scope of the invention further extends to cure-on-demand fillmaterial that can be used for disc nucleus implants, wherein theconductive fill material in injected to conform to the shape of a spacewherein Rf current is then applied to increase the modulus of thematerial on demand to a desired level that is adapted for dynamicstabilization. Thus, the Rf conductive filler material 120 can beengineered to reach a desired modulus that is less than that of ahardened fill material used for bone support. In this embodiment, thefill material is used to support a disc or portion thereof. Thecure-on-demand fill material also can be configured as an injectablematerial to repair or patch a disc annulus as when a tear or herniationoccurs.

The scope of the invention further extends to cure-on-demand fillmaterial that can be used for injection into a space between vertebraefor intervertebral fusion. The injection of fill material can conform toa space created between two adjacent vertebrae, or can be injected intonotches or bores in two adjacent vertebrae and the intervening space,and then cured by application of Rf current to provide a substantiallyhigh modulus block to cause bone fusion.

In any embodiment such as for intervertebral fusion or for bone supportin VCFs, the system can further include the injection of a gas (such ascarbon dioxide) into the fill material before it is injected from a highpressure source. Thereafter, the gas can expand to form voids in thefill material as it is cured to create porosities in the hardened fillmaterial for allowing rapid bone ingrowth into the fill material.

In a related method of the invention, the fill material 120 can beintroduced into the cancellous bone 122 in different aliquots whereineach volume carries a different type of conductive filler, e.g., withdifferent volume percentages of conductive filler or differentdimensions of conductive fillers. In one embodiment, the secondaryaliquots of fill material are not conductive.

In related methods of the invention, the system of the invention can useany suitable energy source, other that radiofrequency energy, toaccomplish the purpose of altering the viscosity of the fill material120. The method of altering fill material can be at least one of aradiofrequency source, a laser source, a microwave source, a magneticsource and an ultrasound source. Each of these energy sources can beconfigured to preferentially deliver energy to a cooperating, energysensitive filler component carried by the fill material. For example,such filler can be suitable chomophores for cooperating with a lightsource, ferromagnetic materials for cooperating with magnetic inductiveheating means, or fluids that thermally respond to microwave energy.

The scope of the invention includes using additional filler materialssuch as porous scaffold element and materials for allowing oraccelerating bone ingrowth. In any embodiment, the filler material cancomprise reticulated or porous elements of the types disclosed inco-pending U.S. patent application Ser. No. 11/146,891, filed Jun. 7,2005, titled “Implants and Methods for Treating Bone” which isincorporated herein by reference in its entirety and should beconsidered a part of this specification. Such fillers also carrybioactive agents. Additional fillers, or the conductive filler, also caninclude thermally insulative solid or hollow microspheres of a glass orother material for reducing heat transfer to bone from the exothermicreaction in a typical bone cement component.

The above description of the invention is intended to be illustrativeand not exhaustive. Particular characteristics, features, dimensions andthe like that are presented in dependent claims can be combined and fallwithin the scope of the invention. The invention also encompassesembodiments as if dependent claims were alternatively written in amultiple dependent claim format with reference to other independentclaims. Specific characteristics and features of the invention and itsmethod are described in relation to some figures and not in others, andthis is for convenience only. While the principles of the invention havebeen made clear in the exemplary descriptions and combinations, it willbe obvious to those skilled in the art that modifications may beutilized in the practice of the invention, and otherwise, which areparticularly adapted to specific environments and operative requirementswithout departing from the principles of the invention. The appendedclaims are intended to cover and embrace any and all such modifications,with the limits only of the true purview, spirit and scope of theinvention.

Of course, the foregoing description is that of certain features,aspects and advantages of the present invention, to which variouschanges and modifications can be made without departing from the spiritand scope of the present invention. Moreover, the bone treatment systemsand methods need not feature all of the objects, advantages, featuresand aspects discussed above. Thus, for example, those skill in the artwill recognize that the invention can be embodied or carried out in amanner that achieves or optimizes one advantage or a group of advantagesas taught herein without necessarily achieving other objects oradvantages as may be taught or suggested herein. In addition, while anumber of variations of the invention have been shown and described indetail, other modifications and methods of use, which are within thescope of this invention, will be readily apparent to those of skill inthe art based upon this disclosure. It is contemplated that variouscombinations or subcombinations of these specific features and aspectsof embodiments may be made and still fall within the scope of theinvention. Accordingly, it should be understood that various featuresand aspects of the disclosed embodiments can be combined with orsubstituted for one another in order to form varying modes of thediscussed bone treatment systems and methods.

1. A method for treating a vertebral fracture, comprising: controllablyapplying energy from an energy source to a bone cement in an injectorsystem via a heating element disposed in the injector system, at least aportion of the injector system having an outlet port positionable withincancellous bone, the applied energy selectively increasing the viscosityof the bone cement; injecting a volume of bone cement having theselectively increased viscosity into the cancellous bone; andcontrolling the viscosity of the cement injected through the injectorsystem via the controlled application of energy so that the bone cementflows into cancellous bone along a flow path between the outlet port anda periphery of the volume, and so at least a portion of the flow pathcomprises bone cement interdigitated with the cancellous bone.
 2. Themethod of claim 1 wherein the injecting step includes injecting the bonecement at a predetermined flow rate into the cancellous bone.
 3. Themethod of claim 1, wherein controlling the viscosity of the cementincludes applying a first level of energy to the bone cement to achievea first desired change in bone cement viscosity, and applying a secondlevel of energy different from the first level to the bone cement toachieve a second desired change in bone cement viscosity.
 4. The methodof claim 1, further comprising monitoring a parameter of the bonecement.
 5. The method of claim 4, wherein the parameter comprising atleast one of temperature and impedance.
 6. The method of claim 1,further comprising modulating the application of energy with acontroller.
 7. The method of claim 6, wherein the modulation is inresponse to a monitored parameter of the bone cement.
 8. The method ofclaim 1, wherein the energy source comprising at least one of a radiofrequency source, a resistive heat source, a laser source, a microwavesource, a magnetic source and an ultrasound source.
 9. A method fortreating a vertebral body, comprising: controllably applying energy froman energy source to a bone cement wherein the application of energyselectively increases the viscosity of the bone cement; and injecting avolume of the bone cement having the selectively increased viscosityinto cancellous bone of the vertebral body wherein the viscosity of thevolume of bone cement is controlled by the controlled application ofenergy; wherein the injected volume of bone cement flows along a flowpath that interdigitates and permeates the cancellous bone, the volumeof bone cement being injected without previously compacting thecancellous bone.
 10. The method of claim 9, wherein the bone cementfollows a natural flow path through the cancellous bone.
 11. The methodof claim 9, wherein the bone cement follows a flow path through thecancellous bone having an outer region that completely surroundsinterdigitated cancellous bone.
 12. The method of claim 9, whereinapplying energy includes applying energy to selected portions of thevolume of bone cement.
 13. The method of claim 9, wherein the bonecement forms a flow impermeable surface on at least a portion of thebone cement.
 14. The method of claim 9, further comprising applyingsufficient energy to the bone cement to substantially acceleratepolymerization of the bone cement.
 15. The method of claim 9, whereinthe viscosity of the bone cement is selectively increased so as toinhibit extravasation in the vertebral fracture.
 16. A method fortreating a vertebral body, comprising: controllably applying energy froman energy source to a bone cement via a heating element in an injectorsystem, the applied energy selectively increasing viscosity of the bonecement; and injecting a volume of the bone cement through an outlet portof the injector system into cancellous bone of the vertebral bodywherein the viscosity of the volume of bone cement is controlled by thecontrolled application of energy; wherein the injected volume of thebone cement flows along a flow path interdigitating and permeating thecancellous bone, an outer region of the flow path surroundinginterdigitated cancellous bone located in the flow path between theouter region and the outlet port.
 17. The method of claim 16, furthercomprising injecting an additional volume of bone cement into thecancellous bone of the vertebral body.
 18. The method of claim 17,wherein injecting the additional volume of bone cement expands at leasta portion of a surface of the initial volume defined by the outerregion.
 19. The method of claim 17, wherein injecting the additionalvolume supports or moves cortical bone.